Method of compacting soil for conducting offshore operations



July 26, 1960 I R. P. KNAPP 2,946,198

METHOD OF COMPACTING son FOR CONDUCTING OFFSHORE OPERATIONS OriginalFiled Dec. 20, 1955 8 Sheets-Sheet 1 FIG. 3.

S an

INVENTQR. Richard P. Kna'pp,

July 26, 1960 R. P. KNAPP METHOD OF COMPACTING son. FOR CONDUCTINGOFFSHORE OPERATIONS 23 Sheets- Sheet 2 Original Filed Dec. 20, 1955 mmmm m m w m Richard P. Knapp,

ATTORNEY July 26, 1960 R. P. KNAPP 2,946,198

METHOD OF COMPACTING SOIL. FOR CONDUCTING OFFSHORE OPERATIONS OriginalFiled Dec. 20, 1955 8 Sheets-Sheet 3 FIG. l3.

FIG. l2.

FIG. ll.

FIG.

IN VEN TOR.

.AIIQR EY.

July 26, 1960 R. P. KNAPP METHOD OF COMPACTING son, FOR CONDUCTINGOFFSHORE OPERATIONS 8 Sheets-Sheet 4 Original Filed Dec. 20, 1955INVENTOR.

Richard P. Knapp,

llllll ATTOR Li WIWIII 8 Sheets-Sheet 5 ONDUCTING R. P. KNAPP METHOD OFCOMPACTING SOIL FOR C OFFSHOFE OPERATIONS Original Filed Dec. 20, 1955llu July 26, 1960 FIG. 27.

INVENTOR. Richard P. Knapp,

ATTY.

July 26, 1960 R. P. KN-APP 2,946,198

METHOD OF COMPACTING son. FOR CONDUCTING OFFSHORE OPERATIONS OriginalFiled Dec. 20, 1955 8 Sheets-Sheet 6 FIG. 28.

50 r -'1, 3 FIG 3| 1 I so 5 I l L .I J

CONTROL INVENTOR. Richard P. Knapp BY Ag P. KNAP TING SOIL FORCONDUCTING IONS PAC OFFSHORE OPERAT 8 Sheets-Sheet 7 TOW LINE INVENTOR.

Richard P. Knapp,

FIG. 34.

ATTORNEY.

July 26, I960 METHOD OF COM Original Filed Dec. 20, 1955 FIG. 33.

July 26, 1960 R. P. KNAPP 2,946,198

METHOD OF COMPACTING son. FOR CONDUCTING OFFSHORE OPERATIONS OriginalFiled Dec. 20, 1955 8 Sheets-Sheet 8 DERRICK INVENTOR. Richard P. Knupp,

ATTORN Y.

,IM. i

FIG. 35.

SEA LEVEL ocean FLOOR I States Patent Office METHOD OF COMPACTING son.FOR CON- DUCTING OFFSHORE OPERATIONS Richard P. Knapp, Houston, Tex.,assignor, by mesne assignments, to Jersey Production Research Company,Tulsa, Okla, a corporation of Delaware Original application Dec. 20,1955, Ser. NO. 554,375. Divided and this application Jan. 28, 1957, Ser.No. 636,769

The present invention is directed to a structure suitable for use inoffshore operations. More particularly, the invention is directed to aportable, stable structure which is easily transportable to a marinelocation. -In its more specific aspects, the invention is directed tomarine structure which has stability and which is easily transportableto an offshore location.

This application is a division of Serial No. 554,375, filed December 20,1955, in the name of Richard P. Knapp entitled Method and Structure ForOffshore Op.- erations.

The present invention may be briefly described as a portable, stablestructure suitable for use in offshore marine operations which comprisesa bottom bearing member having a plurality of interconnected verticallyextending buoyancy columns connected to. the bottom bearing member ontheir lower ends. A platform is supported by the buoyancy columns on theupper ends of the buoyancy columns. Vertically adjustable auxiliarybuoyancy means are arranged on all or a selected of the buoyancy columnswith a portion of the buoyancy means extending inboard of the structureand the remaining portion of the buoyancy means extending outboard ofthe structure. The bottom bearing member may be provided simply as a matbut may be constructed such that it has buoyancy and may be suitablycompartmented and provided with sea chests, valves, and the like forflooding the compartments of the bottom bearing member with water toballast same and with suitable air connections to blow the water fromthe compartments. Suitably the buoyant bottom bearing member may have anopen bottom and buoyancy given thereto by maintaining a selected airpressure therein.

The structure of the present invention is provided with verticallyadjustable spuds arranged in the buoyant columns, such that they may beextended through the lower end of the buoyant columns to serve asmooring and anchoring means by positioning the spuds into the underlyingbottom of the marine location where the structure may be located. Thespuds are vertically adjustable such that they may be extended orretracted into the buoyant columns. The spuds may be extendedor-retracted by employing jacks of the hydraulic type and the like,suitable screw and wedge mechanisms, hydraulic means and the like forraising and lowering the spuds. The spuds may suitably be provided witha hydraulic lock, clamps or pins or other means for locking the spuds inposition as may be desired.

The present invention is also directed to a method for preloading thesoil on which the device of the present invention is positioned.Briefly, in practicing the method of the present invention, thestructure is floated into position with the bottom bearing member oifbottom. The vertically adjustable auxiliary buoyancy means are thenflooded a sufiicient amount to cause the bottom bearing member to sinkto the bottom. The device is then firmly positioned against verticalmovement by driving the spuds downwardly into the soil underneath thebottom bearing member. This is suitably done by exerting hydraulicpressure against the spuds although other means may be employed.Thereafter, the hydraulic pressure is released from the spuds, whichhave now been driven into the soil and which allows the structure tohave some vertical movement but prevents any lateral movement due towave action, and the like.

The auxiliary buoyancy means are then dewatered which allows thebuoyancy means or tanks to rise on the buoyant columns to a point abovemarine bottom such that they may be firmly attached to the columns bysuitable attaching means. The force of the tanks vertically is thenexerted on the columns. The auxiliary buoyancy tanks are then floodedwith Water to the extent that the water level in the auxiliary. buoyancymeans or tanks is greater than sea level. This is accomplished by.pumping water into the auxiliary buoyancy means rather than relyingsolely on the water entering same through the sea chest. -By floodingthe auxiliary buoyancy means, the auxiliary buoyancy means movesdownwardly causing the buoyant columns to move downwardly therewithsince the auxiliary buoyancy means are connected thereto. By adjustingthe level of the water in the auxiliary buoyancy tanks, the columns andbottom bearing member are provided with a preload in excess of thepreloading which will be maintained on the structure during the marineoperations. For example, the preloading on the columns and bottombearing member may be in the range from about 500 to about 2000 poundsper square foot. This preloading depends on the operating load on thebottom. In the Gulf Coast area a preload of 500 to 2000 pounds persquare inch will usually suflice. Ordinarily preloads in the range fromabout 500 to 1000 pounds per square inch will be satisfactory. Ofcourse, it is realized that the preloading in the practice of thepresent invention will depend on the operating load on the sea bottomandmay vary depending on the region where the offshore operations areconducted.

As the auxiliary buoyancy means or tanks sink, the weight thereof bearsdown on the buoyant columns and causes the soil under the mat to becompacted by squeezing moisture from the compacted soil. .The auxiliarybuoyancy tanks may be adjusted with varying amounts of water or preloadto level the structure where the structure is not on an even keel.

In practicing the present invention, the auxiliary buoyancy means ortanks are locked to the buoyant columns for a suflicient length of timeto compact the soil under the bottom bearing means. This time maysuitably range from about 4 hours to about 48 hours. Times from about 4hours to about 24 hours may be satisfactory and preferred.

The spuds are then locked into position against vertical movement bysuitable locking means whichmay be hydraulic pressure exerted againstthe spuds to prevent vertical movement. The auxiliary buoyancy means ortanks are then dewatered to a floating position, unlatched, and removedfrom the buoyant columns. in practicing the method of the presentinvention, a more stable structure is possible than heretofore. ,7

lt is understood that the structure of the present invention maycomprise a plurality of extension supporting members constitutingbuilding blocks made up of interconnected, vertically extending columns.Thus, the platform may be supported on a plurality of building blocks orextension supporting members connected to the bottom bearing members andwhen it is desirable to extend or lower the height of the structure foruse. in

deeper or shallower waterthe platforrnrrnay be removed Patented July 26,1960 a and building blocks or extension supporting members either addedto the structure or subtracted therefrom. The extension supportingmembers comprising the interconnected, vertically extending columnswould be connected to each other, either by welding or by a boltedflange arrangement which would allow easy removal of the extensionsupporting members from or addition of the extension supporting membersto the structure.

It is contemplated that the auxiliary buoyancy means arranged on all ora selected of the buoyant columns may be removable therefrom. In short,the auxiliary buoyancy means may be provided with a slot and latcharrangement for placing same on the buoyant columns or the buoyancymeans may be provided with a removable segment for arranging same on thecolumns. Alternatively, the auxiliary buoyancy means may comprise aplurality of buoyant chambers interconnected and arranged aroundselected or all of the buoyant columns. The buoyancy means may alsocomprise a plurality of buoyant chambers arranged one upon another andseparable from each other such that buoyant chambers may be added toprovide additional buoyancy or buoyant chambers may be subtracted as maybe desired.

Where the buoyancy means are provided with a removable segment, it iscontemplated that the buoyancy means and the segment may be providedwith opposing surfaces defining complementary obtuse and acute angleswith the horizontal axis of the buoyancy means, the sum of the anglesbeing approximately 180. In short, the buoyancy means may have a surfacedefining an obtuse angle and the segment may have a surface defining anacute angle or vice versa, the sum of the angles being approximately180.

It is contemplated that the auxiliary buoyancy means may be inflatablesuch that when it is desired to provide auxiliary buoyancy the auxiliarybuoyancy means would be inflated and when the auxiliary buoyancy is nolonger required the buoyancy means may be deflated as desired.

Thus, the present invention relates to a portable marine platform whichprovides a stable foundation for machinery, drilling equipment, storagetanks, and the like, a base for salvage operation located over a body ofwater. The platform involving the structure may be moved with or withoutthe drilling equipment and the like from one water location to anotheras desired or it may be converted to an improved type of permanentmarine structure. The platform is easily adjusted to permit safe use ina wide range of water depths.

The invention is particularly suitable to well drilling operations suchas oil and/or gas or sulfur wells and may be used with an auxiliaryvessel or platform or suitably may be self-contained to provide thenecessary living quarters and warehouse facilities to conduct suchmarine operations.

The present invention will be further illustrated by reference to thedrawing in which:

Fig. l is a side elevation of the platform structure;

Fig. 2 is a horizontal section along line 22 of Fig. 1;

Fig. 3 is a vertical section along line 3-3 of Fig. 1;

Fig. 4 is a vertical section along line 4-4 of Fig. 1;

Fig. 5 is a side elevation of the platform structure in a normal welldrilling position;

Fig. 6 is a side elevation, showing buoyancy transport units attachedand the platform ready for movement to a new drilling site;

Fig. 7 is a side elevation, showing buoyancy transport units attachedand the platform in a normal moving position;

Figs. 8 and 9 are side elevations, showing larger or multiple buoyancytransport units attached and the platform structure in a normal movingposition;

Fig. 10 is a side elevation of the platform structure in an alternatedrilling position with buoyancy transport units attached and submerged;

Fig. 11 is a side elevation of the platform structure .4 shown in Fig.10 after moving to deeper water and the addition of one truss bay orextension member;

Figs. 12 and 13 are side elevations of the platform structure shown inFig. 10 after moving to deeper water and the addition of two and threetruss bays or extension members;

Fig. 14 is a side elevation of the platform in a drilling position withbuoyancy transport units attached;

Fig. 15 is a plan view of the platform shown in Fig. 14, showing theworking deck area and one arrangement of the buoyancy transport units;

Fig. 16 is a vertical section through the platform along line 16-46 ofFig. 15;

Fig. 17 is a horizontal section through the platform along line 1717 ofFig. 14;

Fig. 18 is a side elevation of the platform in a drilling position witha buoyancy transport units removed;

Fig. 19 is a fragmentary view showing a buoyancy transport unit composedof several individual, vertical, buoyant vessel compartments;

Fig. 20 is a sectional top view of Fig. 19;

Fig. 21 is a horizontal section similar to Fig. 20 showing the use of aslotted barge or chamber for a buoyancy transport unit;

Fig. 22 is a vertical section through an inflatable buoyancy transportunit and a transport column;

Figs. 23, 24, and 25 are top and side elevations of another type ofremovable buoyancy transport unit;

Fig. 26 is a side elevation of the platform in a permanent position withbuoyancy transport units and transport columns removed;

. Fig. 27 is a plan view of the' platform shown in Fig. 26;

Fig. 28 is a side elevation of the platform with the buoyancy means intransporting position;

Fig. 29 is a sectional view taken along the line 29-29 of Fig. 28;

Fig. 30 is an enlarged plan view of one of the buoyancy means of Figs.28 and 29;

Fig. 3 1 is a view partly in section taken along the line 31-41 of Fig.30;

Figs. 32 and 33 are top and side views, respectively, of another type ofbuoyancy transport means;

Fig. 34 is a perspective View of the platform, equipped with drillingderrick, being transported;

Fig. 35 is a perspective view of the platform of Fig. 34 in a drillingposition and with the buoyancy means removed.

Referring now to the drawings in which identical numerals will beemployed to designate identical parts, and particularly to Figs. 1 to 4,the structure comprises a working structure generally indicated by thenumeral 11 which is of rectangular form and having a generally flatworking surface generally designated by the numeral 12. The workingsurface or platform 12 is suitably supported by longitudinal ortransverse structural members 13 which are supported by a trussworkindicated generally by the numeral 14 composed of vertically extendingcolumns 15, diagonal members 16, and horizontal girt members 17. Thestructure is also provided with buoyant columns 18. The trusswork 14 andthe buoyant columns 18 ter urinate in a bottom bearing member .19 whichis of general rectangular form with a suitable opening or openings 20for the conducting of drilling operations and the like. The bottombearing member is suitably constructed of longitudinal and transversestructural members and may be provided with suitable compartments,chambers, and the like, 21.

Extending through the columns 18 are bottom penetrating mooring spudsindicated generally by the numeral 10 which penetrate into the soilbelow the bottom bearing member 19 to provide resistance to lateralmovement, overturn, and vertical sinkage of the structure. The spuds 10are adjustable vertically and may be extended or retrusted as may bedesired,

While the platform structure 12 is shown to have a square working deckand a square bottom bearing member with four buoyant columns forming thefour corners of a square horizontal section, it is possible to haveother configurations but it is preferred to have a square structurebecause it provides the most stable structure for a given structuralweight. It is to be understood, however, that other shapes andconfigurations may be used and may be preferable where structural weightis a secondary consideration. For example, a rectangular plan with thelength greater than the width may be more desirable where the width islimited by existing land facilities and a greater length is necessary toobtain the required working deck or bearing bottom member area.

As pointed out supra, it is not necessary that the bottom bearing member19 be a watertight structure and it is preferable that the btotombearing member 19 have as little buoyancy as possible when the structureis in the moving position. For maximum stability during movingoperations the bottom bearing member should be completely flooded oropen to the sea, with buoyancy limited to the volume of water displacedby the structural members. As pointed out before some watertightcompartmentation may be desirable for the storage of liquids or to floatthe platform on the surface of the sea for delivery, overhaul and/orrepairs.

Referring now to Fig. 5, the structure is shown in a normal drillingposition with a drilling rig 22 mounted on the platform 12. The spudshave been extended and have been driven into the underlying land 23 withthe platform 12 being located a suitable distance above the water level24 for safe operations. The structure of Fig. 5 may be converted from astable, temporary, and portable drilling platform to a permanentplatform as shown in Figs. 26 and 27 by driving bearing piles, such as25, through the vertical columns and/or through the buoyant column 18.The number of bearing piles, the depth of penetration, and the size maybe determined by the soil and oceanographic conditions encountered atthe site of the permanent installation.

It is to be noted that Figs. 26 and 27 are modified structures 11ahaving a platform 12a. As shown bythe plan view in Fig. 27, the platform12a of the structure 11a has a cross shape which provides a maximum areafor this particular shape.

Referring now to Figs. 6 to 9, auxiliary buoyancy means generallyindicated by the numeral 26 are attached to the buoyant columns 18 suchthat the auxiliary buoyancy means 26 are vertically adjustable thereinand extend inboard and outboard of the structure. By providing theauxiliary buoyancy means to extend both inboard and outboard, greaterstability of the structure is provided than would be otherwise if theauxiliary buoyancy means were completely inboard or completely outboardof the structure. The dotted lines in Fig. 6 show the auxiliary buoyancymeans 26 to be vertically adjustable and the position assumed in movingthe structure from the underlying land bottom 23. It is to be noted inFig. 6 that the vertically adjustable spuds 10 have been retracted intothe interior of the columns 18 and the structure 11 is in position to bemoved oflshore. As the auxiliary buoyancy means 26 are dewatered, orinflated if a collapsible type of buoyancy means is used, and withbuoyancy provided on the columns 18, suflicient buoyancy is given to thestructure 11 to float same off the sea bottom 23. It is to be noted thatthe auxiliary buoyancy means 26 assume the position as shown in Fig. 7at sea level to provide a floating structure.

As illustrated in Figs. 8 and 9, additional numbers of auxiliarybuoyancy means 26 may be added to the structure as desired to float thestructure 11 higher in the water or to give a greater freeboard asshown. The plurality of auxiliary buoyancy means may be suitably lockedone to the other by suitable locking means and are separable one fromthe other and are superimposed on each other by arranging same eitherbelow or above the original buoyancy means as provided in Figs. 6 and 7.Of course, it is realized and understood that buoyancy means may beremoved as desired to reduce the freeboard. After the structure has beenraised to a moving position, as shown in Figs. 7, 8, and 9, it may thenbe towed or moved to the next desired location and then again sunk tothe underlying land bottom 23 and anchored thereto by reversing thesteps of the operation as has been described.

As illustrated in Figs. 10 through 13, inclusive, the structure 11 isadjustable in height and is suitably constructed of extension supportingmembers or building block sections which are generally designated by thenumeral 30. In Fig. 10 the structure 11 with the drilling rig 22 isshown landed on bottom 23 with the spuds 10 sunk in the earth and withthe bottom bearing member 19 resting on the bottom 23. Auxiliarybuoyancy means 26 are resting on the bottom 23, having been filled withwater. Assuming that it is desired to raise the level of the platform 12above the water level 24 preparatory toa move into deeper water, thedrilling rig 22 and platform 12 would be removed and another buildingblock 30 would be brought into'position and placed on the uppermost ofthe building blocks 30. The building blocks 30 would be suitablyconnected to those already in place, such as by welding or by boltedflanges and then the platform 12 and drilling rig 22 would be replacedon the structure, as shown in Fig. 11. Thereafter, as illustrated inFigs. 6 to 9, the structure would be moved from water having a depth ofabout 33 feet, as shown in Fig. 10, with the platform 12 about 35 feetabove water to water having a depth of about 50 feet with platform 12being about 40 feet above the water level 24, as shown in Fig. 11. Thespuds 10 would again be lowered and the structure could then be usedagain for drilling operations and the like.

In Figs. 12 and 13 illustrations are given for identical building blocks30 to provide a structure with respect to Fig. 12 usable in water ofabout 73 feet depth providing a platform about 24 feet above waterlevel. :In Fig. 13, the structure is illustrated which is suitable fordrilling operation in foot water.

Referring now to Figs. 14 through 16 it is to be noted that theauxiliary buoyancy means 26 are of general cylindrical shape and extendboth inboard and outboard of the structure 11. The spuds 10 are showndriven into the underlying land bottom 23 and with the auxiliarybuoyancy means 26 resting on bottom. In Figs. 14 through 16 theauxiliary buoyancy means 26 are arranged permanently on the structure 11surrounding the columns 18 and 15. Fig. 17 is a plan view showing theopening 20 of the structure 11. When the auxiliary buoyancy means 26 areemployed, it will be necessary to provide means for introducing waterinto and removing water from the auxiliary buoyancy means 26. To thisend a flexible connection such as 31 provided with a valve 32 may bearranged to extend from the platform 12 to the buoyancy means 26. Thisflexible connection 31 may be a suitable hose which may be of deformablematerial and reinforced with metallic members or may be a braided metalhose and the like. The flexible member 31 may extend inboard andoutboard of the structure to provide air pressure to the members 26 orto relieve air pressure therefrom. It is also likely that water may alsobe pumped into the buoyancy means 26 through line 31 or sea cocks may beprovided in each of the buoyancy means 26 and controlled by a valve rodextending up to platform 12.

Fig. 18 is a view similar to Fig. 16 but shows the buoyancy means 26removed therefrom and the spuds 10 driven into the land bottom 23.

In Figs. 19 and 20, a modified auxiliary buoyancy means 26b comprised ofa plurality of inter-connected vessels 260 are shown. The interconnectedvessels 26c are suitably connected by structural members 33 and'arrangedaround selected or all of the columns 18 as maybe desired. It will beapparent fromFigs. 1 9 and 20 that the '7 vessels 26c may easily beremoved from around any or all of the columns 18 as may be desired.

In Fig. 21 a different type of removable auxiliary buoyancy means isillustrated in which a barge or vessel, such as 34, provided with a slot35 is arranged around the columns 18 and locked thereon by means of alocking mechanism, such as pin 36. It is to be noted that the vessel 34may be easily removed by removing the locking mechanism 36 and guidingthe vessel 34 oil the column 18. It is to be noted that the vessel 34extends both inboard and outboard of the structure.

Another type of auxiliary buoyancy means is shown in Fig. 22 in which aninflatable member 37 is arranged on the columns 18 to surround same. Theinflatable member 37 extends both inboard and outboard of the structureand may suitably be deflated and left to rest on the bottom bearingmember 19 when not in use and inflated when in use. To this end, asuitable flexible connecting member, such as 31, extending to theplatform 12 and provided with a valve 32 may be used for inflation anddeflation as desired. 7

Referring to Figs. 23, 24, and 25 another type of removable auxiliarybuoyancy means is provided. Auxiliary buoyancy means 38 is provided witha removable pieshaped segment 39 which may suitably be removed from thecolumns 18 to allow floating off of the auxiliary buoyancy means 38therefrom. The auxiliary buoyancy means 38 and the pie-shaped segment 39thereof are provided with complementary sloping surfaces 4! and 41 whichdefine complementary acute and obtuse angles with the horizontal axis ofthe member 38. By virtue of providing sloping surfaces 40 and 41 thesegment 39 may suitably be pinned and latched to the auxiliary buoyancymeans 38. Passengeways 42 are provided to receive pins, not shown, tolatch the auxiliary buoyancy means 38 and segments 39 thereto.

Referring specifically to Figs. 29 and 30, the buoyancy transport means51 are composed of two equal or approximately equal tank sections 52which are joined at one side by a hinged connection 53. The two sections52 provide an annular central opening 54 large enough to accommodate thebuoyancy columns 18. The sections 52 are opened and closed by hydraulicmeans generally indicated by numeral 55 which may comprise a piston andcylinder arrangement operated by a suitable pump. The sections 52 may belocked together in a closed position by a pin such as 56. The buoyancytransport means 51 may also be of the type shown in Figs. 23, 2.4, and25.

Each of the sections 52 of the buoyancy transport means is provided witha sea cock controlled by a valve wheel 57. The sections are alsoprovided with a deep well type pump 58 provided with a conduit 59projecting into the tank section for the purpose of dewatering thesections when desired. The Water in the sections may be pumped out bymeans of the pump 58, or the water may be forced out by pumping in :airand opening the sea cocks by valve wheel 57. The tank sections 52 areprovided with vents 60 for the release of air when flooding the sectionswith water.

As shown in Figs. 30 and 31, the buoyancy means 51 are provided withlatching means 61 for the purpose of latching the buoyancy means to thecolumns 18. This latching means is each comprised of two upright racks62 having adjustably mounted thereon a cross bar 63 for vertical andhorizontal movement. The cross bar 63 is provided on one end thereofwith a U-shaped clevis 64 which engages with one of a series of verticalspaced apart annular shoulders 50 of the columns 18. Engagement of theselatching means and dewatering or flooding of the buoyancy means affordsa lifting or lowering force to be exerted on the platform structure 11.

The device as shown in Figs. 28 through 31 operates and may be used in asimilar fashion to the other embodiments shown.

Referring now to Figs. 32 and 33, a structure, such as 11, provided witha platform 12 and columns 18 has a plurality of auxiliary buoyancy means70 removably arranged on the columns 18. These auxiliary buoyancy means70 are generally rectangular in shape with segments, such as 71, cut outtherefrom to allow the auxiliary buoyancy means 70 to be placedremovably on the columns '18. After the auxiliary buoyancy means 70 havebeen placed in position, they may be suitably locked therein by suitablelocking means indicated generally by the numeral 72. This lockingmechanism may suitably be a member which will make a snug fit around thecolumn 18 to prevent lateral movement and to allow vertical movement asmay be desired. For example, a horizontally retractable member which hasan outer arcuate surface, such as indicated, may be positioned incontact with the outer periphery of the columns 18 to lock the auxiliarybuoyancy means 70 against lateral movement but for vertical movementthereon as desired. It is understood that the means 70 may be lockedagainst vertical movement as well.

In practicing the present invention, the structure 11 would be floatedinto position and the auxiliary buoyancy means 26 would then be floodedwith a sufficient amount of water to cause the structure to sink to thesea bottom 23 with the mat 19 on bottom. Thereafter, the spuds 10 wouldbe sunk or forced into the earth 23 by suitable hydraulic means, notshown. Hydraulic pressure is then released which will allow somevertical movement of thestructure 11. The auxiliary buoyancy tanks 26are then dewatered which allow them to rise on the columns 18 to afloating position. The auxiliary buoyancy means 26 are then latched orlocked to the columns 18 such that any force exerted by the tanks 26will be exerted on the columns 18. The auxiliary buoyancy tanks 26 arethen flooded with water or have water pumped in to a level above the sealevel suflicient to provide a preload on the bottom bearing member 19 inexcess of that which will be employed on the structure 11. As theauxiliary tanks 26 sink with the columns .18, the soil making up thebottom 23 is compacted under the bottom bearing member 19 to causemoisture to be squeezed out therefrom. The tanks 26 provide preload forthe time indicated and then the spuds it) are locked into positionagainst vertical movement. The tanks 26 are then dewatered to a floatingposition, unlatched from the columns 18 and then removed therefrom asdesired.

Figs. 34 and 35 are perspective views illustrating the structure 11which could be any of the embodiments as described in the transportingposition with the buoyancy means attached and in the anchored positionwith the buoyancy means removed.

The present invention is of considerable utility and advantage in that astable marine structure is provided which is easily removable and may beanchored permanently at a desired marine location. The structure hasstability in that the auxiliary buoyancy means extend both inboard andoutboard of the structure. Furthermore, the structure is adjustable inheight and may be removed fromshallow to deep water or vice versa andused therein. Furthermore, the structure is of considerable utility inthat the auxiliary buoyancy means may be arranged permanently on thestructure or releasable therefrom.

The nature and objects of the present invention having been completelydescribed and illustrated, what I wish to claim as new and useful and tosecure by Letters Patent is:

1. A method for compacting the soil under an offshore marine drillingstructure provided with a flat rectangular bottom bearing member whichcomprises floating the structure into position with the bottom bearingmember oil marine bottom, sinking said structure until the bottombearing member rests on marine bottom, anchoring said structure againstlateral movement by driving spuds into the marine bottom at the cornersof said structure, preloading said bottom bearing member on the cornersthereof a sufficient amount to provide a load on the bottom bearingmember in excess of the operating load exerted on the bottom bearingmember, said preloading being effected by exerting weight on the bottombearing member from a point above marine bottom with water filled tanksfora suflicient length of time to compact the earths structure beneaththe bottom bearing member, locking said structure to said spuds againstvertical movement relative to the soil, and then removing said preloadexerted by said tanks from said bottom bearing member.

2. A method in accordance with claim 1 in which the [time is in therange from about 4 to about 48 hours.

3. A method in accordance with claim 1 in which the 10 preloading'amount is in the range from about 500 to about 2000 pounds per squarefoot of said bottom bearing member.

4-. A method in accordance with claim 1 in which the structure is lockedagainst vertical movement by hydraulic pressure.

References Cited in the file of this patent UNITED STATES PATENTS 10 Re.24,346 Dawson Aug. 20, 1957 2,248,0 5 1 Armstrong July 8, 1941 2,574,140Boschen Nov. 6, 1951 2,750,750 Kuss et a1. June 19, 1956

